NEET UG, JEE Main Physics - Volume II

41 Pages·2016·0.89 MB·English

by  Target Publications

For all Agricultural, Medical, Pharmacy and Engineering Entrance Examinations held across India.

NEET-UG / AIPMT & JEE (Main)

Physics

Salient Features

• Exhaustive coverage of MCQs subtopic wise.
  • ‘4024’ MCQs including questions from various competitive exams.
• Includes solved MCQs from MHT CET 2016, NEET P-I and P-II 2016,

JEE (Main) 2015 & 16, AIPMT 2015 & Re-Test.
  • Various competitive exam questions updated till latest year.
• Concise theory for every topic.

• Neat and authentic diagrams.

• Hints provided wherever relevant.
  • Topic test at the end of each chapter.
• Important inclusions: Knowledge bank and Googly questions

Solutions/hints to Topic Test available in downloadable PDF format at

www.targetpublications.org/tp10063

  Printed at: Repro India Ltd. Mumbai

© Target Publications Pvt. Ltd.
No part of this book may be reproduced or transmitted in any form or by any means, C.D. ROM/Audio Video Cassettes or electronic, mechanical
including photocopying; recording or by any information storage and ret rieval system without permission in writing from the Publisher.
P.O. No. 32715

10063_11010_JUP
PREFACE
Target’s “NEET Physics Vol-II” is compiled according to the notified syllabus for NEET-UG & JEE (Main), which
in turn has been framed after reviewing various state syllabi as well as the ones prepared by CBSE, NCERT and
COBSE.
The book comprises of a comprehensive coverage of Theoretical Concepts & Multiple Choice Questions. The flow
of content & MCQ’s is planned keeping in mind the weightage given to a topic as per the NEET-UG & JEE (Main)
exam.
MCQ’s in each chapter are a mix of questions based on theory, numerical and graphical. The level of difficulty of
these questions is at par with that of various competitive examinations like CBSE, AIIMS, CPMT, JEE, AIEEE,
TS EAMCET (Med. and Engg.), BCECE, Assam CEE, AP EAMCET (Med. and Engg.) & the likes. Also to keep
students updated, questions from most recent examinations such as AIPMT/NEET, MHT CET, K CET, GUJ CET,
WB JEEM, JEE (Main), of years 2015 and 2016 are exclusively covered.
Unique points are represented in the form of Notes at the end of theory section, Formulae are
collectively placed after notes for quick revision and Shortcuts are included to save time of students while
dealing with rigorous questions.
An additional feature of Knowledge Bank is introduced to give students glimpse of various interesting concepts
related to the subtopic.
Googly Questions are specifically prepared to develop thinking skills required to answer any tricky or higher
order question in students. These will give students an edge required to score in highly competitive exams.
Topic Test has been provided at the end of each chapter to assess the level of preparation of the student on a
competitive level.
We are confident that this book will cater to needs of students of all categories and effectively assist them to achieve
their goal. We welcome readers’ comments and suggestions which will enable us to refine and enrich this book further.

All the best to all Aspirants!
Yours faithfully
Authors

No. Topic Name Page No.
1 Electrostatics 1
2 Current Electricity 108
3 Magnetic Effect of Electric Current 181
4 Magnetism 248
5 Electromagnetic Induction and Alternating Current 302
6 Electromagnetic Waves 371
7 Ray Optics 397
8 Wave Optics 476
9 Interference of Light 494
10 Diffraction and Polarisation of Light 521
11 Dual Nature of Matter and Radiation 554
12 Atoms and Nuclei 596
13 Electronic Devices 664
14 Communication Systems 737

Note: ** marked section is not for JEE (Main)
Chapter 01 : Electrostatics
01

Electrostatics

1.1 Electric charges and their conservation 1.12 Equipotential surface

  1.2 Coulomb’s law-force between two point 1.13 Electric potential energy of a system of two
  charges point charges and of ** electric dipoles in

  electrostatic field
1.3 Superposition principle, forces between

multiple charges 1.14 Conductors and insulators, Free and bound

charges inside a conductor
  1.4 Continuous distribution of charges

  1.15 Dielectrics and electric polarization
1.5 Electric field, Electric field lines, Electric
  field due to a point charge 1.16 Capacitors and Capacitance

1.6 Electric dipole and electric field due to a 1.17 Capacitance of parallel plate capacitor with

dipole and without dielectric medium between the

plates.
  1.7 Torque on a dipole in uniform electric field  

  1 .18 Combination of capacitors in series and
1.8 Electric Flux
    parallel

1.9 Gauss’ theorem and its applications

1.19 Energy stored in a capacitor
  1.10 Electric potential and **potential difference  
**1.20 Van de Graaff generator

1.11 Electric potential due to a point charge, a

dipole and a system of charges

1 .1 Electric charges and their conservation  Charging by induction
i. The redistribution of charges within a
 Electrostatics: body due to the presence of a nearby
The study of electricity or electric charges at charge is called electrostatic induction.
rest is known as electrostatics. ii. The charged body induces an opposite

charge on the neutral body without
 Charge:
actually touching it.
i. The property of particles like protons and
For eg: Attraction of paper bits towards a comb
electrons which produces electrical
is due to the charging of comb by
influence is called as charge.
rubbing it against dry hair. When the
ii. It is a scalar quantity.
charged comb is brought near the paper
iii. Formula: q = It
bits, it induces an opposite charge at the
where q is charge, I is current, t is time.
end of paper nearer to the comb resulting
iv. Unit: coulomb in SI system and stat
in attraction.
coulomb in CGS system
1 C = 3  109 stat coulomb  Quantisation of charge:
stat coulomb is also called electrostatic i. Charge (q) on a body is always equal to
unit (e.s.u.) of charge. the integral multiple of electronic charge
v. Dimensions: [M0 L0 T1 A1] (e).
vi. There are two types of charges: positive  q =  ne
and negative. where n = 1,2,3,…
vii. Like charges repel, unlike charges attract. ii. Each electron bears a charge equal to
viii. The electric charge is additive in nature –1.6  10–19 C.

and is invariant.
ix. Accelerated charge radiates energy.  Conservation of charges:
x. Charge cannot exist without mass. i. For an isolated system, the net charge
xi. Charge does not experience any force due always remains constant.
to electric field produced by it. ii. Net charge can neither be created nor be
xii. A body can be charged by rubbing or destroyed in any isolated system.
conduction or induction. iii. Transfer of charges is possible.

1
Physics Vol‐II (Med. and Engg.)
1 .2 Coulomb’s law  force between two 1.3 Sup erposition principle, forces
point charges between multiple charges

 Coulomb’s law:  Superposition principle:
i. Force of attraction or repulsion between i. Total force acting on a given charge due
two charges is directly proportional to the to number of charges is the vector sum of
product of the charges and inversely
the individual forces acting on that charge
proportional to the square of the distance
due to all the charges.
between them.
ii. Consider number of charges q , q , q ….
qq 1 2 3
F  1 2 are applying force on a charge q
r2

Net force on q will be
qq
 F = C 1 2
r2 F FF ....F F
net 1 2 n1 n
where, q and q are charges separated by
1 2
distance r. q

ii. In air, C = 1 in SI system and C = 1 in r1 r
n
4
CGS system. 0 q1 r2 r3 rn–1 qn
In any medium, C 1 in SI system q2 q qn–1
4k 3
0
1 iii. The magnitude of the resultant of two
and C = in CGS system.
k electric forces is given by,
iii. The force between two charges in any
medium, Fnet
1 qq F
F = 1 2 2
4k0 r2  

iv. In vector notation, force on q2 due to q1 is F1
given as,
F21 = 41k qr1q32r12 Fnet = F12+F22+2F1F2cosθ
0 12 Fsinθ
 and tanα= 2
where, r12 is the position vector from q1 F1+F2cosθ
to q .
2 iv. The force between any two charges is not
Force on q due to q is given as,
1 2 affected by the presence or absence of
 1 qq 
F = 1 2 r other charges.
12 4k r3 21
0 21
  Forces between multiple charges:
where, r is the position vector from
21 i. Principle of superposition is used to
q to q .
2 1 calculate electric force on a charge due to
v. Coulomb’s force between charges is
other charges in the vicinity.
central force and acts along the line
joining the charges. ii. For N point charges q1, q2, …. , qN located
vi. Coulomb’s force between the two charges   
at positions r ,r ,....r with respect to
is independent of presence of other 1 2 N
charges in the surrounding. 
origin respectively, total force F
1
 Dielectric constant: experienced by charge q due to all other
1
Dielectric constant is defined as the ratio of
charges is given by,
permittivity of any medium () to the permittivity
    
of free space (0). F1F12F13F14........F1N
i.e., k =  iii. Using vector form of Coulomb’s law,

0  
  = k        
where0, 0 = 8.85  1012 C2/Nm2 and F141 q1q2 r1r23 q1q3 r1r33 ........qlqN r1rN3
1 = 9  109 Nm2/C2 or farad metre–1 (Fm–1)  0 r1r2 r1r2 r1rN 
4
0

22
Chapter 01 : Electrostatics
iii. Force on charge q due to volume charge
1.4 Continuous distribution of charges 0
distribution is,
 Continuous distribution of charges:  q dv
F 0  rˆ'
i. A system of closely spaced electric 4 r'2
charges form a continuous charge 0
distribution. 1.5 Electric field, Electric field lines,
ii. On macroscopic level, quantisation of Electric field due to a point charge

charges is ignored. For a charged body
with reasonable size, its charge  Electric field:
distribution is treated as continuous. i. The space around charge in which its
iii. The continuous distribution can be electric force can be experienced is called
categorized as linear, surface and volume electric field.
charge distribution. ii. The electric field is a vector quantity

introduced as an intermediary between
 Linear charge density: charges.
i. When charge is distributed along a line, Charge  field  charge
charge distribution is called linear.
iii. The electric field is characteristic of
ii. Linear charge density, q charge or system of charges and
L independent of the test charge placed at a
where, L is length of rod. point.
iii. Unit: coulomb metre–1 (Cm–1) iv. The electric field is quantified by electric
iv. Dimensions: [M0 L–1 T1 A1] field intensity.

 Surface charge density: 
i. When charge is distributed over a surface,  Electric field intensity E:
 
charge distribution is called surface
i. Electric field intensity at any point in an
charge distribution.
electric field is defined as the force acting
ii. Surface charge density,
per unit test charge at that point in an
q electric field.

A ii. Electric field intensity is a vector quantity
where, A is surface area. and represents strength of electric field.
iii. Unit: coulomb metre–2 (Cm–2) 
iv. Dimensions: [M0 L–2 T1 A1] iii. Formula: E F where, q is test charge
q 0
0
 Volume charge density: iv. Unit: newton coulomb–1 (NC–1) or
i. When charge is distributed over the volt metre–1 (Vm–1) in SI system.
volume of an object, it is called volume v. Dimensions: [M1 L1 T–3 A1]
charge distribution.
vi. It is also called as electric field strength or
ii. Volume charge density,
electric field.
q vii. In the presence of dielectric, electric field

V 1
decreases and becomes times its value
where, V is volume.
k
iii. Unit: coulomb metre–3 (Cm–3)
in free space.
iv. Dimensions: [M0 L–3 T1 A1]

 Electric field due to a point charge:
 Force due to various charge distribution:
i. Consider an isolated point charge q at the
i. Force on charge q due to line charge
0 origin. Force experienced by test charge q
0
distribution,

at distance r is,
 q dl
F 0  rˆ'  1 qq
4 r'2 F 0 rˆ
0 4 r2
where, r is distance between charge 0
element and point under consideration. ii. Th e electric intensity at the point is given
rˆ'is unit vector directed from charge as,
element to the point. 
 F
ii. Force on charge q0 due to surface charge E
distribution, q
0
F q0 dsrˆ'  E 1 q rˆ
40 r'2 40 r2

3
Physics Vol‐II (Med. and Engg.)
  Electric field intensity due to an electric
iii. The magnitude of E follows inverse
dipole at a point on its axial line (End on
square law.
position):
iv. The electric field due to point charge is
i. A line passing through the positive and
spherically symmetric.
negative charges of the electric dipole is
 Electric field lines: called the axial line of the electric dipole.
i. The imaginary path along which a free ii. Consider an electric dipole consisting of
positive charge moves when placed in an two point charges ‘– q’ and ‘+ q’
electric field is called as electric lines of separated by a distance 2l as shown in
force. figure.
ii. They start from a positive charge and end
on a negative charge. Axial Line
Y
iii. The tangent to the line of force at any
  
point gives the direction of the electric – q + q E1 E E2
field intensity E at that point. A O B C P D X
iv. Two lines of force do not intersect each l l
other. r
v. The lines of force are normal to the 
E at a point on the axial line
surface of a charged conductor at any
point. The medium between the electric dipole
vi. Lines of force do not pass through a and the observation point has dielectric
conductor. Hence the electric field inside a constant k.
conductor is always zero. Lines of force 
iii. If E is the electric intensity at P due to
can pass through an insulator. 1
charge ‘– q’, then
vii. Electric lines of force are crowded
together where the field is strong and E  1 q (ˆi)
widely separated from each other where 1 4 k (rl)2
0
the field is weak.

E is represented both in magnitude and
viii. The lines of force are under tension and 1
tend to shrink. This explains why two direction by PC.
unlike charges attract each other. 
iv. If E is the electric intensity at P due to
ix. The lines of force exert a lateral pressure 2
charge ‘+q’, then
on one another. This explains why like
charges repel each other. E  1 q ˆi
2 4 k (rl)2
1.6 Electric dipole and electric field due 0
to a dipole E is represented both in magnitude and
2
 Electric dipole: direction by PD.
i. System of equal and opposite charges v. Resultant intensity,
separated by a small fixed distance is E = E – E
2 1
called dipole.
ii. Electric dipole moment p = q(2l) = 4q k (r1l)2 (r1l)2ˆi
where, 2l = dipole length 0
q = magnitude of either of the charge. 2(q2l)r 
= i
 4 k(r2l2)2
iii. In vector form, pq2lpˆ 0
 1 2pr 
 E i
The direction of p is from negative 4 k (r2l2)2
0
charge to positive charge. vi. If dipole is of very small length, i.e.,
iv. Unit:
 1 2p 
l < < r, E i
coulomb metre (Cm) or debye in SI unit.
4 k r3
stat C cm in CGS unit. 0
v. Dimensions: [M0 L1 T1 A1] For vacuum E = 1 2p
vi. It is a vector. 40 r3
vii. The electric field produced by a dipole is vii. The direction of electric field intensity due
known as dipole field. to electric dipole at a point on its axial line
viii. The dipole field has a cylindrical is always along the direction of the dipole
symmetry. moment.

44
Chapter 01 : Electrostatics
 Electric field intensity due to an electric 
 1 p
dipole at a point on the equatorial line (Broad viii. In vector form, E
4 k r3
side – on position): 0
 
i. Equatorial line of an electric dipole is a Negative sign indicates E and p are in
line perpendicular to the axial line and opposite direction.
passing through a point mid-way between 1 p
For vacuum E =
the charges of the dipole. 4 r3
0
ii. Consider an electric dipole consisting of ix. Using parallelogram law of vectors,
two point charges ‘– q’ and ‘+ q’ E = 2 E1 cos 
separated by distance 2l as shown in i.e., Eaxial = 2 Eequator
figure.
 Electric field intensity at a general point due
D to short electric dipole:

E i. Consider a short electric dipole with
 2
R E  P dipole moment p placed in vacuum. Let

O be the mid-point of dipole and line OP
C E1 makes an angle  with p.

r2l2 r r2l2  E2
B E  A


E 
  2 E
– q + q P 1
A O B (r, )
l l r
 p cos 
E at a point on equatorial


iii. The medium between the electric dipole
and the observation point has dielectric – q O p + q

constant k.
p sin 
iv. If E is the electric field intensity at P due
1
to charge ‘– q’, then ii. For any general point P, axial line
component of electric field intensity is,
1 q
E =
1 4 k r2l2 E  1 2pcos along PA.
0 1 4 r3
 0
E is represented both in magnitude and Equatorial line component of electric field
1
direction by PC. intensity is, E  1 psin along PB.
v. If E is the electric field intensity at P due 2 4 r3
2 0
to charge ‘+ q’, then iii. Resultant electric intensity is,
1 q 2
E2 = 40k r2l2 E2 E12E2241 rp3 (4 cos2 + sin2)
0
( BP2 = OP2 + OB2) 1 p
E 3cos21
 4 r3
E is represented both in magnitude and 0
2
iv. From the above figure,
direction by PD.
E tan
 tan  = 2 =
vi. Resultant intensity E at P is,
E 2
1
E = E cos  + E cos 
1 1 q22l  l   = tan–1 1 tan
= cos  2 
40k (r2l2)3/2  r2l2  v. Special cases:
1 p a. Case I: When P lies on the axial
=
4 k (r2l2)3/2 line of the dipole,  = 0.
0
vii. If dipole is of very small length, i.e., 1 p
E = 3cos21
l < < r, 4 r3
0
1 p 1 2p
E = E =
4 k r3 4 r3
0 0

5
Physics Vol‐II (Med. and Engg.)
tan0 vi. Unit:
tan  = = 0
2 Nm in SI system
  = 0 dyne – cm in CGS system
b. Case II: When P lies on the vii. Dimensions: [M1 L2 T–2 A0]
equatorial line of the dipole,
1.8 Electric flux

 = 90.
E = 1 p 3cos2901  Electric Flux:
4 r3 i. The number of electric lines of force
0
1 p passing through a given area is called as
E =
4 r3 electric flux.
0
ii. It is a scalar quantity.
tan90
tan  = = 
iii. The electric flux , through a surface
2
q
  = 90 enclosing ‘q’ is,  =
1 .7 Torque on a dipole in uniform electric field iv. dUynniet:- cNmm22/s/Cta tocro Vul-omm bin0 i Sn IC sGysSt esmys. tem.
i. An electric dipole consisting of two charges
v. Dimensions: [M1 L3 T3 A1]
+ q and – q separated by distance 2l is held in
vi. Electric flux is the dot product of electric

a uniform external electric field E at an angle intensity vector and surface area vector,

 as shown. ds
 
 = E.ds

B F
 = Edscos
+ q 

2l 
p

E vii. For a closed body, outward flux is taken to
be positive and inward flux is negative.
 A  viii. Electric flux per unit area is called the flux
–F
– q C density.
ix. Electric flux is maximum when electric field
is normal to the area ds
Dipole in uniform electric field
i.e., d = Eds.

ii. Two equal and opposite forces act on dipole, x. Electric flux will be minimum when electric
field is parallel to the area
 
|F||F|qE
i.e., d = zero.

Hence net force is zero.

 Tube of force:
iii. Net torque  acts on dipole about an axis
i. The number of lines of
passing through the mid point of dipole.
force grouped together to
 = F  2l sin
form tube like structure is
= qE  2l sin
called as tube of force.
  = pE sin

  
iv. In vector form, pE
Tube of force

v. Special cases:
ii. A tube of force originating from unit
a. Case I:
positive charge is called unit tube of force
When  = 0, then  = pE sin 0 = 0
or Faraday’s tube of force.
The electric dipole is in stable
iii. Tube of force has the same properties as
equilibrium.
line of force.
b. Case II:
iv. The number of tubes of force originating
When  = 90, then  = pE sin 90
1 1
= pE (maximum value) from unit positive charge is = .
c. Case III:   k
0
When  = 180, then  = pE sin 180 = 0 v. The number of tubes of force originating
The electric dipole is in an unstable q
from charge q is .
equilibrium.  k
0

66
Chapter 01 : Electrostatics
 Tube of induction: E
i. Tube of force irrespective of permittivity
E E
of medium is called tube of induction. 2 1

ii. Only one tube of induction originates

from unit positive charge whatever may
P

be the surrounding medium. r
P1 O P2
 Normal Electric Induction (NEI):
i. The number of tubes of induction passing + + + + + + + + + + + + + + + + + +
normally through unit area is called as
normal electric induction. ii. The electric field of every point in plane
ii. Formula: normal to wire is radial and its magnitude
depends only on radial distance r.
NEI = E = k E
0
iii. Consider a circular closed cylinder of
iii. Unit:
radius r and length l with infinitely long
C/m2 in SI system and
line of charge as its axis as shown in
stat C/cm2 in CGS system
figure.
 Total Normal Electric Induction (TNEI): E

i. TNEI is defined as number of tubes of
nˆ nˆ
induction passing normally through a nˆ

given area. P

ds
ii. The number of tubes of induction passing
nˆ r nˆ
normally through charge ‘q’ is
+ + + + + + + + +
N = q
k
0 nˆ nˆ
iii. No. of tubes of induction passing normally
through unit area is k E, l
0
TNEI =  k 0 E ds cos iv. Contribution of curved surface of cylinder
  towards electric flux,
=  k  Eds
0
 
iv. Unit: coulomb in SI system statcoulomb Eds = E (2rl)
in CGS system s
v. Dimension: [M0L0 T1 A1] where (2rl) is area of curved surface of

cylinder.
1.9 Gauss’ theorem and its applications
v. Total electric flux through cylinder,
 Gauss’ theorem:  = E (2rl)
E
i. Total flux through a closed surface is Charge enclosed in cylinder q = l.
equal to 1 times the total charge vi. From Gauss’ theorem,  = q
0 E 0
enclosed by that surface.
l
 E (2rl) =
  q
ii. Eds 
0

0 
iii. Gauss’ theorem holds good for any closed  E =
2 r
surface irrespective of its shape or size. 0
vii. The electric intensity is inversely
iv. The imaginary surface which encloses the
1
charge or charged body is called proportional to the radius r. E 
Gaussian surface. r

viii. If  > 0, direction of electric field at every
 Application of Gauss’ Theorem:
point is radially outwards.
Electric field due to an infinitely long straight
If  < 0, direction of electric field at every
wire:
point is radially inwards.
i. Consider an infinitely long thin wire with

uniform linear charge density . Let P In this case, E is due to charge on entire
1
and P be line elements placed at equal wire while charge enclosed by Gaussian
2
distance on either side of origin ‘O’. surface is only   l.

7